brain-cavity

If this wretched little remnant were a coil of explosive fuse within the brain-cavity itself, which any jar might set off, it could hardly be richer in possibilities of danger.

Preventable Diseases Woods Hutchinson 1896

Such a feature would imply, on the supposition that the heads were of the ordinary size, a large brain-cavity, and so an unusual volume of brain, which is generally a concomitant of high intellectual power.

The Seven Great Monarchies Of The Ancient Eastern World, Vol 5. (of 7): Persia The History, Geography, And Antiquities Of Chaldaea, Assyria, Babylon, Media, Persia, Parthia, And Sassanian or New Persian Empire; With Maps and Illustrations. George Rawlinson 1857